This relates generally to electronic devices, and more particularly, to maintaining accurate timing information on portable electronic devices.
In general, it is desirable for electronic devices be able to provide accurate timing information. Users often rely on an electronic wristwatch or other portable electronic devices such mobile telephone devices, laptop computers, and tablet computers to provide the correct time. These devices typically include a time keeping component such as a quartz crystal oscillator. A quartz crystal oscillator is a component that uses the mechanical resonance of a vibrating piezoelectric material to create an electrical signal with a very precise frequency. A digital counter is controlled by this electrical signal and outputs a value that can be translated to useful timing information in the form of hours, minutes, and seconds.
Crystal oscillators are generally accurate to ±15 seconds per month. Environmental factors such as temperature, humidity, pressure, and vibration, as well as battery voltage and the age of the crystal itself, can affect the accuracy of the oscillators. Several techniques already exist to synchronize devices to a common time base, such as use of the Network Time Protocol (NTP) to synchronize to atomic clocks via the Internet or use of a Global Positioning System (GPS) receiver to synchronize to the timing information transmitted by each GPS satellite.
In some situations, a user may operate more than one electronic device. In such situations, it may be inefficient for multiple devices to have to separately synchronize to a common time base via NTP or GPS. It may be desirable for only one of the devices to first obtain accurate timing information, and then to transfer that accurate timing information to other associated devices.